Permanent magnetic switch



Jan. 26, 1965 J. P. JONES, JR 3,167,624

PERMANENT MAGNETIC SWITCH Filed Feb. 27, 1962 FIG. I

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FIG. 3. FIG. 4.

INVENTOR. JOHN PAUL JONES,JR.

United States Patent 3,167,624 PERMANENT MAGNETIC SWITCH John PaulJones, Jr., Wynnewood, Pa., assignor to Navigation Computer Corporation,a corporation of Pennsylvania Filed Feb. 27, 1962, Ser. No. 175,942 8Claims. (Cl. 20087) This invention relates to electrical switches and inparticular to simple and reliable switches of the magnetic detent type.

Most electrical switches are constructed so they operate with snapaction. Snap action swithches have a fast make and break which preventsarcing when high voltages are switched. Moreover, snap action switcheshave a certain initial resistance which releases suddenly to produce apositive switching action. This latter feature decreases the chance forhuman error during operation. There are many different switches of thesnap action type. Many of these bounce after making initial contact, anundesirable characteristic, particularly in low voltage level electroniccircuitry. In addition, most are complicated and therefore expensive tomanufacture, particularly if a high packing density is desirable, as ina keyboard or multiswitch panel for operating transistor circuitry.

t is therefore an object of the present invention to provide an improvedswitch which is simple to construct and reliable in operation.

It is another object of the present invention to provide an improvedswitch of the magnetic detent type which provides positive switchingaction in a small amount of space.

It is yet another object of the present invention to provide animproved, simple, and reliable switch which is particularly adaptablefor use with printed circuits and transistor circuitry.

A magnetic detent switch embodying the invention comprises a push-buttonwhich is fastened to a permanent bar magnet through an aperture in ametallic keyboard panel. The contact portion of the switch comprises twofiat metallic contacts which are mounted in place on, or are part of, aprinted circuit board. A leaf spring contact is permanently mounted inengagement with one of the flat contacts and is moved in engagement, bya wiping action, with the other flat contact when the push-button isdepressed. In a momentary contact embodiment of the invention, themagnet is attracted to the metallic keyboard panel when the push-buttonis released, thus disengaging the leaf spring from the one contact. Inanother embodiment of the invention, the push-button is held in the onposition by a metallic member which holds the magnet in place until acurrent is passed through the metallic member. In still anotherembodiment, a pair of leaf springs are employed and the push-button andmagnet assembly are arranged to alternately engage and disengage the twosprings from their contacts.

The novel features that are considered characteristic of this inventionare set forth with particularity in the appended claims. The inventionitself, however, both as to its organization and method of operation, aswell as additional objects and advantages thereof, will best beunderstood from the following description when read in connection withthe accompanying drawing, in which:

FIGURES l and 2 are side elevational views, partially in section, of amagnetic detent switch embodying the invention;

FIGURE 3 is a side elevational view, partially in section, of anotherembodiment of a magnetic detent switch in accordance with the invention;and

FIGURE 4 is a side elevational view, partially in section, of a magneticdetent switch employing two contacts and embodying the invention.

Referring now to the drawing wherein like parts are indicated by likereference numerals throughout the figurea, and referring particularly toFIG. 1, the push-button 8 of a magnetic detent switch embodying theinvention is mounted above an opening in a metallic panel 10. The panel10, for example, is a keyboard panel of a piece of multiswitchelectronic equipment. It would be constructed typically of steel. Thepush-button is mounted on an angle to the plane of the panel 10 asillustrated. The push-button 8 has retaining grooves on both ends whichextend beyond the opening in the panel. The remaining portion of thepush-button 8 extends through the opening in the panel 10. A flat,substantially square, permanent bar magnet 12 is attached to the bottomof the push-button assembly. Normally, therefore, the magnet 12 isattracted to the steel panel 10 and remains in the position shown inFIG. I.

The contact portion of the switch includes a semicircular leaf spring 14which is constructed of a conducting material. One end of the leafspring 14 is riveted (as shown) or soldered to a printed circuit board16. The rivet passes through a first printed circuit element 18 which islocated between the printed circuit board 16 and the under surface ofthe leaf spring. The printed circuit element 18 and a second printedcircuit element 20, mounted on the board 18 beneath the other end of theleaf spring 14 form the contacts of the switch.

The operation of the switch is more clearly illustrated in FIG. 2,reference to which is now made. Normally, the bar magnet 12 is attractedto the steel panel 10 and stays firmly in the position shown in FIG. 1.When the push-button 8 is manually depressed, however, the magnet 12 ismoved downwardly and strikes the leaf spring 14. This action causes theleaf spring 14 to make contact with the printed circuit element 20 witha wiping action, thus closing the switch. When pressure is removed fromthe push-button 8, the bar magnet 12 is attracted to the steel panel 10and returns to its original position. The leaf spring 14 at this timealso returns to its original position and the switch is opened.

The embodiment of the invention illustrated in FIG. 3, reference towhich is now made, provides a hold position for the switch. This isaccomplished by providing a metallic strip 22 on the circuit board 16.The strip 22 would be constructed of a magnetic material such as iron.Accordingly, when the push-button S is depressed as shown in FIG. 3, oneend of the bar magnet 12 is attracted to the iron strip 22 and is heldin the position shown, which is the closed position. In this position,the leaf spring 14 contacts the contact 20 by a wiping action, as inFIG. 2. The bar magnet 12 can be released from this position and theswitch opened by passing a current through the iron strip 22 as by abattery 23. A magnetic field is thus created around the strip 22 whichrepels the magnet 12. This bucking field is sufiicient in magnitude torelease the magnet 12 from the strip 22. The magnet 12 is then attractedto the sheet keyboard panel 10 and returns to its original position,similar to the position illustrated in FIG. 1. In this position, theswitch is opened.

The switch illustrated in FIG. 4 is arranged so that either one of twoswitch contacts can be closed by depressing a push-button 24. Thepush-button 24 is V- shaped and is attached, as in FIGS. 1, 2, and 3, toa permanent bar magnet 12, which in this embodiment of the inventioncould be slightly longer than the magnets used in the switches of theembodiments previously described. The push-button and magnet assembly ispivoted by means of pivot pin 26. The switch illustrated in FIG. 4includes two substantially identical contact assemblies 28 and 30 whichare attached to the printed circuit board 16 in the same manner as wasdescribed for the prior figures.

In operation, when the right hand portion (as viewed in the drawing) ofthe V-shaped push-button 24 is depressed, the right end of the barmagnet 12 is moved downwardly and strikes the leaf spring of theright-hand contact assembly 30. The spring thus contacts, with a wipingaction, the contact on the printed circuit board 16. When the left handportion of the push-button 24 is depressed the left end of the barmagnet 12 (which had been previously in contact with the steel panel 10)is moved downwardly, thus releasing the right hand contact assembly tothe off position and causing the leaf spring of the left hand contactassembly to contact the contact on the printed circuit board.

The embodiment of the invention illustrated in FIG. 4 thus permits twoseparate circuits to be alternately opened and closed with onepush-button. Such a switch would be useful, for example, in changing thebinary output of a flip flop circuit from a 1 to a and vice versa.

The switches embodying this invention are simple to construct. Closetolerances are not needed, making the switches economical tomanufacture. The switches operate by a snap action and provide aninitial resistance to their manual operation, thereby reducing humanerrors in their operation. A Wiping contact is provided. The initialwiping action absorbs the initial contact energy through friction. Thisfeature avoids the undesirable bounce of many of the prior art switches.In addition, the switches are especially adaptable to Printed Circuittype wiring configurations, which are economical, and are being used inan increasing percentage of all electronic equipment. Thus, reliability,simplicity, economy of manufacture, and ease of operation characterizethe switches embodying the invention.

What is claimed is:

1. A magnetic switch comprising, in combination, a panel, a pushbuttonhaving a bottom surface which engages the top surface of said panel whensaid pushbutton is depressed and said switch is closed, means connectingsaid pushbutton to a permanent magnet through an aperture in said panel,said magnet being normally attracted to said panel and in fixedengagement thereto when said switch is open, and normally open contactmeans including a spring-like member arranged to be flexed in responseto the downward movement of said pushbutton.

2. A magnetic switch comprising, in combination, a metallic push-buttonpanel, a tapered push-button, the underside of which engages the topsurface of said panel when said push-button is depressed and said switchis closed, means connecting said push-button to an elongated permanentmagnet through an aperture in said panel, said magnet being normallyattracted to the underside of said metallic panel and in fixedengagement thereto when said switch is open, and normally opencontactmeans including a spring-like member mounted below said magnet andarranged to be flexed in response to the downward movement of saidpush-button and magnet to close said switch and to provide upwardpressure on said magnet when said push-button is released and saidswitch is open.

3. A magnetic switch comprising, in combination, an aperturedpush-button panel, a tapered push-button mounted above the aperture insaid panel, the underside of said push-button engaging said panel whensaid push-button is depressed and'said switch is closed, a permanent barmagnet located below the aperture in said panel, means connecting saidpush-button and said magnet through said aperture to provide an integralpush-button assembly, a circuit board mounted in a plane parallel tosaid push-button panel and below said magnet, a pair of electricalcontacts mounted in spaced relationship on said circuit board, aspring-like member, means connecting one end of said spring-like memberto one of said contacts, the other end of said spring-like member beingarranged in spaced and close relationship to said other contact abovesaid other contact, said spring-like member being arranged to be flexedin response to the downward movement of said pushbutton assemblytoprovide a wiping contact of said other end with said other contact toclose said switch.

4. A magnetic switch as defined in claim 3, wherein said push-buttonpanel is metallic and said bar magnet is attracted to said panel whensaid switch is opened to release said spring-like member.

5. A magnetic switch as defined in claim 3, wherein a strip of magneticmetal is mounted on said circuit board adjacent to said one of saidcontacts and said magnet contacts said strip of metal when saidpush-button assembly is moved downwardly to hold said switch in theclosed position, and means providing a current through said strip toopen said switch.

6. A magnetic switch comprising, in combination, an aperturedpush-button panel, a tapered push-button mounted above the aperture insaid panel, the underside of said push-button engaging said panel whensaid pushbutton is depressed and said switch is closed, means connectingsaid push-button to a bar magnet through said aperture, said magnetbeing normally attracted to said panel when said switch is open, acircuit board mounted below said magnet and said panel in a planeparallel thereto, a pair of electrical contacts mounted on said circuitboard, a semicircular metallic spring member, means connecting one endof said spring member to one of said contacts and in such relationshipto said other of said contacts that the other end of said spring membercontacts the other of said contacts in response to the downward movementof said push-button and magnet to close said switch.

7. A magnetic switch as defined in claim 6, wherein metallic means areprovided adjacent said one of said contacts ,tO hold said switch in theclosed position and means are provided to pass a current through saidmetallic means to open said switch. 7

8. A magnetic switch comprising, in combination, an aperturedpush-button panel, a \l-shaped push-button mounted above the aperture insaid panel, pivoted means connecting said push-button to an elongatedbar magnet through said aperture, a circuit board mounted below saidmagnet and said panel in a plane parallel thereto, a first and a secondpair of electrical contacts mounted on said circuit board, a first and asecond metallic spring member, means connecting one end of said firstspring member to one of said first pair of electrical contacts and insuch relationship to said other of said first pair of electricalcontacts that the other end of said first spring member contacts theother of said first pair of electrical contacts in response to thedownward movement of one end of said magnet, and means connecting oneend of said second spring member to one of said second pair ofelectrical contacts and in such relationship to said other of saidsecond pair of contacts that the other end of said second spring membercontacts the other of said second pair of electrical contacts inresponse to the downward movement of the other end of said magnet.

References Cited in the file of this patent UNITED STATES PATENTS2,770,697 Kellett Nov. 13, 1956 2,816,254 Canepa Dec. 10, 1957 2,962,571Zanichowsky Nov. 29, 1960 2,971,068 Wegner Feb. 7, 1961 3,052,778 KatheSept. 4, 1962

1. A MAGNETIC SWITCH COMPRISING, IN COMBINATION, A PANEL, A PUSHBUTTONHAVING A BOTTOM SURFACE WHICH ENGAGES THE TOP SURFACE OF SAID PANEL WHENSAID PUSHBUTTON IS DEPRESSED AND SAID SWITCH IS CLOSED, MEANS CONNECTINGSAID PUSHBUTTON TO A PERMANENT MAGNET THROUGH AN APERTURE IN SAID PANEL,SAID MAGNET BEING NORMALLY ATTRACTED TO SAID PANEL AND IN FIXEDENGAGEMENT THERETO WHEN SAID SWITCH IS OPEN, THE NORMALLY OPEN CONTACTMEANS INCLUDING A SPRING-LIKE MEMBER ARRANGED TO BE FLEXED IN RESPONSETO THE DOWNWARD MOVEMENT OF SAID PUSHBUTTON.